JPH0832303B2 - Carbon dioxide immobilization method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a carbon dioxide immobilization method, and in particular, immobilizes carbon dioxide to prevent environmental destruction such as global warming due to carbon dioxide in the atmosphere. On how to do.

[Conventional technology]

Combustion of fossil fuels in power plants, boilers for general industries, etc. has increased the carbon dioxide concentration in the atmosphere, and in recent years the global warming phenomenon called the greenhouse effect has become a problem. As a method of discarding carbon dioxide without releasing it to the atmosphere to prevent an increase in the concentration of carbon dioxide in the atmosphere, or as a method of discarding carbon dioxide after recovering it from the atmosphere,
The following methods have been reported.

1) Dissolve carbon dioxide in seawater and dump it in the ocean. The seawater in which carbon dioxide is dissolved has a larger specific gravity than the surrounding seawater, so it sinks to the ocean floor.

2) Since liquid carbon dioxide has a larger specific gravity than the surrounding seawater under the temperature and pressure in the deep sea with a depth of 3,000 m or more,
Discard as liquid carbon dioxide in the deep sea more than 3,000m.

[Problems to be Solved by the Invention]

In the conventional method 1) mentioned in the preceding paragraph, seawater in which carbon dioxide is dissolved may spread over a wide range due to the flow of seawater in the ocean, which may affect the ecosystem of marine organisms. In addition, the conventional method 2) requires large power for liquefying carbon dioxide and further guiding the liquid carbon dioxide to a depth of 3,000 m or more in the deep sea. May spread.

In view of the above-mentioned conventional state of the art, the present invention does not diffuse carbon dioxide recovered from the combustion exhaust gas or the atmosphere into seawater or freshwater, and does not affect the ecosystem of marine organisms safely. It is intended to provide a method of stably fixing carbon dioxide.

[Means for solving the problem]

The present invention is to produce carbon dioxide hydrate by contacting carbon dioxide with seawater or fresh water under the pressure and temperature required for carbon dioxide hydrate formation, and the carbon dioxide hydrate is under stable conditions in seawater or freshwater. It is a carbon dioxide immobilization method characterized by being immersed in

First, the relationship between the pressure generated by carbon dioxide hydrate and the temperature will be described with reference to FIG.

In FIG. 1, the K _VS value is the equilibrium data of carbon dioxide hydrate, and the conditions for generating carbon dioxide hydrate are satisfied at the pressure and temperature at which this K _VS value becomes 1.0 or less.

Table 1 shows the relationship between the water depth and temperature at which carbon dioxide hydrate is generated in the general ocean. If the water depth is deep, the pressure is high, so carbon dioxide hydrate can be generated even if the water temperature corresponding to it is high.

Next, the specific gravity of carbon dioxide hydrate and seawater will be described.

The specific gravity of carbon dioxide hydrate is about 1.129,
It is known that it is hardly affected by temperature and pressure. The specific gravity of seawater at atmospheric pressure is about 1.03, and the specific gravity of fresh water is smaller than that. Even if the water depth increases and the pressure increases, the increase in the specific gravity of water is small and can be ignored with respect to the specific gravity of carbon dioxide hydrate. If the carbon dioxide hydrate thus produced is left in seawater or fresh water, it will sink naturally, and if it is an ocean, it will be deposited on the seabed and carbon dioxide can be fixed stably and stably.

[Action]

Carbon dioxide is pressurized and mixed with seawater or fresh water in seawater or freshwater satisfying the pressure and temperature conditions for producing carbon dioxide hydrate to generate carbon dioxide hydrate. Carbon dioxide hydrate has a specific gravity of 1.12
Since it is about 9 which is larger than the specific gravity of seawater or freshwater, it sinks to the bottom of the water. When placed in the ocean, it varies depending on the sea area, but in the sea near Japan, deeper than 200 to 500 m, the pressure and temperature conditions for carbon dioxide hydrate formation are satisfied.

Figure 2 shows the vertical distribution of water temperature in February in the waters around Japan. ○ indicates 32.5 ° north latitude and 13 east longitude approximately 100km south of Cape Shio
Kuroshio region at 5.5 °, △ indicates 37.5 ° north latitude about 200km north of Tottori,
Tsushima Sea basin at 134.5 ° east longitude, □ indicates approximately 150km southeast of Cape Erimo
Shows the Oyashio region at 41.5 ° north latitude and 144.5 ° east longitude.

The shaded area in FIG. 2 indicates the range in which carbon dioxide hydrate is produced according to Table 1. According to Fig. 2, in February in Japan, at a latitude of 41.5 ° N, 144.5 ° east, at a depth of more than 120 m, at a latitude of 37.5 ° N, at a depth of 134.5 °, at a depth of more than 220 m, and a latitude of 32.5 ° , 500 in the sea area of 135.5 ° east longitude
It is possible to generate carbon dioxide hydrate at depths deeper than m.

Fig. 3 shows the vertical distribution of water temperature in August in the three waters around Japan similar to Fig. 2.

The shaded area in FIG. 3 indicates the range in which carbon dioxide hydrate is produced according to Table 1. According to Fig. 3, carbon dioxide hydrates can be produced at a depth of more than 160m in the sea area of 41.5 ° north latitude and 144.5 ° east longitude in August of Japan, and 37.5 ° north latitude and 134.5 east longitude 134.5.
It is possible to generate carbon dioxide hydrate at a depth of more than 220 m in the sea area of ゜, and at a depth of more than 450 m in the sea area of latitude 32.5 ゜ north and 135.5 ℃ east longitude.

As shown in Fig. 2 and Fig. 3, the seabed satisfies more stable conditions for carbon dioxide hydrate as compared with the upper part of the sea. Therefore, the carbon dioxide hydrate deposited on the seabed is kept stable.

It is also possible to generate carbon dioxide hydrate on the ground or at the sea and dump it into the sea. In this case, the generated carbon dioxide hydrate is kept so that it does not melt or vaporize until it is introduced into the sea with stable conditions, and the carbon dioxide hydrate is submerged in seawater with stable temperature and pressure conditions. , If it is deposited on the seabed, the carbon dioxide hydrate will be retained on the seabed in a stable state.

Example 1 Example 1 of the present invention will be described with reference to FIG. 4 and Table 2.

Carbon dioxide gas 1 is boosted to 25 kg / cm ² gauge pressure by booster ^{2 and} 200 m in the water area of north latitude 41.5 ° east longitude 144.5 °
To the carbon dioxide hydrate generator 4 installed at the water depth. The temperature of the seawater 5 at the depth where the carbon dioxide hydrate generator 4 is installed is 2 ° C in February and 3 ° C in August,
It has sufficient temperature and pressure conditions to generate carbon dioxide hydrate. The carbon dioxide hydrate generated by the carbon dioxide hydrate generator 4 sinks in seawater and is deposited on the seabed.

Example 2 Example 2 of the present invention will be described with reference to FIG. 5 and Table 3.

Carbon dioxide gas 1 is boosted to 25 kg / cm ² gauge pressure by booster ² , cooled to 3 ° C by cooler 4 and led to carbon dioxide hydrate generator from line 5, while freshwater or seawater at 3 ° C. The pressure of 6 is increased to 20 kg / cm ² gauge pressure by the pump 7, and is guided to the carbon dioxide hydrate generator 9 to generate carbon dioxide hydrate. This carbon dioxide hydrate is passed through the carbon dioxide hydrate carrier 11 and the descending pipe 12 of the carbon dioxide hydrate into seawater, while maintaining the state of the carbon dioxide hydrate 41.5 ° north latitude 14 ° E
It leads to a water depth of 200 m in the 4.5 ° area. 200m depth of water in this area
The temperature is 2 ° C in February and 3 ° C in August, and the carbon dioxide hydrate is in a stable state. The carbon dioxide hydrate sinks in the sea, accumulates on the seabed, and is kept stable.

〔The invention's effect〕

As described above, the method for fixing carbon dioxide of the present invention collects carbon dioxide in the combustion exhaust gas and the atmosphere,
In order to prevent the increase of carbon dioxide in the atmosphere, compared with the conventional method of dissolving recovered carbon dioxide in seawater or discarding it as liquid carbon dioxide into the ocean, carbon dioxide is not diffused in the ocean or fresh water. Since it can be stably deposited as carbon hydrate in certain places, it can prevent the impact on the ecosystem of the ocean or freshwater.

Further, compared with the method of dumping as liquid carbon dioxide into the ocean or fresh water, the power for throwing into sea water or fresh water can be significantly reduced, and it is effective for fixing a large amount of carbon dioxide.

[Brief description of drawings]

Fig. 1 shows the equilibrium diagram of carbon dioxide hydrate, and Fig. 2 shows 2
Chart showing the vertical distribution of water temperature in the waters near Japan and the range of carbon dioxide hydrate formation in March, Fig. 3 is the chart showing the vertical distribution of water temperatures in the waters near Japan in August, and the range of carbon dioxide hydrate formation, and Fig. 4 is the book FIG. 5 is an explanatory diagram of a first embodiment of the invention, and FIG. 5 is an explanatory diagram of a second embodiment of the present invention.

Claims (1)

[Claims] 1. A method for producing carbon dioxide hydrate by contacting carbon dioxide with seawater or fresh water under the pressure and temperature required for producing carbon dioxide hydrate, wherein the carbon dioxide hydrate is stable in seawater or A carbon dioxide immobilization method characterized by being immersed in fresh water.